How to Split a Subdirectory to a New Git Repository and Keep the History

 

(modified from: https://ao.ms/how-to-split-a-subdirectory-to-a-new-git-repository-and-keep-the-history/)

Say, original local path is ~/allMyCode

1) origin repo to check out the branch with all the subdirectory history, eg. master

    git checkout master

2) clone a copy

    git clone  ~/allMyCode  ~/newSubset

    cd ~/newSubset

3) in new clone, remove all but the sub directory (below is a one-liner)

    git filter-branch --prune-empty --subdirectory-filter relative/path/to/subdirectory current_branch_name

4) if the new clone is a branch other than 'master', make it the new 'master'

    git branch -m master

5) remove untracked leftovers, such as ignored/hidden files/folders (WARNING: make sure you have backup)

    git clean -fdx

6) fix remote repo URL    // assume new repo empty

    git remote set-url origin  {newRepoURL}

7) push to new repo

    git push -u origin master